1. Field of the Invention
The invention relates to an orthodontic head gear used for applying traction forces for producing posterior movement of the maxillary molars and arch. More particularly, the invention relates to orthodontic head gear which may be used to selectively produce bilateral or unilateral posterior movement of the maxillary molars and arch independent of the movement of the patient's head without applying a substantial force to the maxillary molars and arch in a direction not parallel to the direction of posterior movement.
2. Description of the Prior Art
Angle, U.S. Pat. No 523,192, discloses an orthodontic head gear having an arch bow which is attached by a ball and socket joint to a face bow. The ball and socket joint is permanently mounted in a plane which bisects the arch bow into symetric parts. Unlike the present invention, Angle's head gear may not be used for producing unilateral posterior movement of the maxillary molars and arch.
Knapp, U.S. Pat. No. 664,412, discloses an orthodontic head gear incorporating a pair of rotatable joints that are permanently connected respectively to an arch bow and a face bow of the head gear in a plane bisecting the arch bow into symetric parts. The individual rotatable joints are rotatable in a single plane but are disposed with respect to the arch and face bow to permit universal movement of the arch bow with respect to the face bow. Knapp's head gear, unlike the present invention, may not be used for producing unilateral posterior movement of the maxillary molars and arch.
MacDowell, U.S. Pat. No. 741,687, discloses an orthodontic head gear having an arch bow which is attached to a face bow by a pivotal coupling disposed in a plane bisecting the arch bow into symetric parts. Unlike the present invention, MacDowell's head gear may not be used for producing unilateral posterior movement of the maxillary molars and arch.
Broussard et al., U.S. Pat. No. 3,866,322, disclose an orthodontic head gear having a rotatable coupling disposed between an arch bow and a face bow. The coupling is not rotatable in orthogonal directions. The rotatable coupling is symetrically disposed with respect to a plane bisecting the arch bow into symetric parts. Broussard et al's apparatus may not be used for producing unilateral posterior movement of the maxillary molars and arch.
A commercially available orthodontic head gear sold by Unitek Corporation as the "Unilateral Zwemer Swivel" permits the unilateral posterior movement of the maxillary molars and arch. This device incorporates a swivel coupling between a point of attachment of a face bow to an arch bow. The coupling is not rotatable in orthogonal directions. Unlike the present invention, this device may not be selectively used for producing unilateral or bilateral posterior movement of the maxillary molars and arch. Moreover, the swivel coupling does not permit movement of the patient's head in orthogonal directions without the application of a substantial force to the maxillary molars and arch in a direction not parallel to the direction of posterior movement of the maxillary molars and arch.